1. Field of the Invention
The present invention relates to a method of manufacturing a nozzle plate, and to a liquid droplet ejection head and an image forming apparatus, and more particularly, to a method of manufacturing a nozzle plate used for an ejection surface of a print head of an inkjet type image forming apparatus, or the like.
2. Description of the Related Art
The print head of an inkjet type image forming apparatus has a plurality of nozzles formed in a nozzle plate which constitutes an ejection surface opposing the recording medium. The shape of the nozzles which eject ink droplets onto the recording medium is liable to affect the size and the ejection speed, and the like, of the ink droplets, and therefore, the nozzles should be formed to a high degree of accuracy. If a linear section is formed at each of the outlet portions of the nozzles in the nozzle plate, then it is possible to improve the linear travel characteristics of ink droplets ejected.
Japanese Patent Application Publication No. 2001-30500 discloses a method of manufacturing a nozzle plate of this kind. FIGS. 10A to 10F are diagrams showing the method of manufacture described in Japanese Patent Application Publication No. 2001-30500. A silicon substrate 160 shown in FIG. 10A is prepared, and a boron layer 171 is formed on one surface of the silicon substrate 160, as shown in FIG. 10B. This boron layer 171 acts as an etching stopper. Thereupon, as shown in FIG. 10C, the other surface of the silicon substrate 160, on which a boron layer 171 is not formed, is covered with a photoresist 172, or the like (i.e., masking is performed), and is then patterned. Wet etching is then carried out using a crystal anisotropic etching solution, as shown in FIG. 10D. Thereby, the surface which is not formed with the boron layer 171 is etched in a square pyramid shape, and the tapered section 151A of a nozzle 151 is formed. The photoresist 172, and the like, is then removed. Next, as shown in FIG. 10E, the boron layer 171 is covered with a photoresist 175, or the like (masking), and is then patterned, whereupon dry etching is carried out to form a linear portion of the nozzle. Thereupon, as shown in FIG. 10F, the photoresist 175, and the like, is removed, and consequently the nozzle plate 161 is completed.
However, there are the following possibilities in manufacture methods of this kind.
More specifically, in the method of manufacturing a nozzle plate disclosed in Japanese Patent Application Publication No. 2001-30500, since crystal anisotropic wet etching is used, then the process is dependent on the crystalline orientation of the silicon substrate 160 and hence the tapered section 151A of the nozzle 151 is limited to a square pyramid shape. Moreover, there are also limitations on the angle of taper. Furthermore, since the tapered section and the linear section of a nozzle are formed by carrying out etching from the front surface side and the rear surface side of the silicon substrate 160 respectively, then divergence of the central axis positions can occur between the tapered section of the nozzle and the linear section of the nozzle.